Consistent Atomic Geometries and Electronic Structure of Five Phases of Potassium Niobate from Density-Functional Theory

Table 4

Lattice parameters , , and , angle , ratios and , equilibrium unit-cell volume , atomic displacements in percent of , and total-energy difference per formula unit with respect to cubic calculated with different exchange-correlation functionals for the monoclinic phase of . Data in brackets represent relative deviations from the experimental values in percent.

	LDA	PBE	PBEsol	AM05	RTPSS
(Å)	3.940 ()	3.983 ()	3.961 ()	3.958 ()	3.984 ()	3.991
(Å)	3.972 ()	4.104 ()	4.023 ()	4.045 ()	4.049 ()	4.046
(Å)	3.970 ()	4.098 ()	4.020 ()	4.041 ()	4.047 ()	4.017
(°)	89.91 ()	89.66 ()	89.82 ()	89.76 ()	89.81 ()	89.89
	0.9919 ()	0.9705 ()	0.9846 ()	0.9785 ()	0.9839 ()	0.9864
	0.9924 ()	0.9719 ()	0.9853 ()	0.9795 ()	0.9844 ()	0.9935
()	62.13 ()	66.99 ()	64.06 ()	64.70 ()	65.28 ()	64.86
K	1.260	2.194	1.736	1.971	1.942
Nb	0	0	0	0	0
O1	3.571	5.906	4.626	5.234	4.771
O2	3.208	5.583	4.262	4.876	4.443
O3	3.197	5.679	4.263	4.890	4.446
(eV)

[47]; measured at 298 K.